Process of producing a screened work copy of an original to be reproduced



Patented: Feb. 7, 1939 PROCESS OF PRODUCING A SCREENED WORK COPY OF AN ORIGINAL TO BE RE- rnonucnn Wilhelm Schupp, Berlin, Germany, assignor oi one-third to Paul A. Hennig, Hohokus, N. 3., and one-third to Sydney Koppel, New York,

No Drawing. Application June 11, 1937, Serial No. 147,631

4 Claims. (Cl. 95-5) For reproducing black-white drawings, pictures etc., I have already proposed to use a positive or negative screened work copy of the original which copy is photographically transferred to a printing plate and which has been obtained by the aid of a screened negative and two continuous-tone negatives; the continuous-tone nega- ,tives serve as controlling means and compensate the flattening of 'the tint values due to the subm division of the screened negative into dots. In

this process films'are preferably used as sensitive carriers.

With regard to the three mentioned negatives the following conditions are to be considered.

15 The main or screened negative generally shall not have well defined dots; the shadow dots (in the lightest portions of the negative) must be essentially larger than normally usual and the lights (the larkest portions of the negative) must 20 be closed a little more than in case of screened.

negatives hitherto used in the chemigraphy.

In the first continuous-tone negative the lights sitive film, the index of gradation of which is I yery high (steep characteristic curve), and by utilizing a developer which automatically limits 30 the blackening within the lightest portions.

The second continuous-tone negative is obtained from a sensitive film with a mean or less high index of gradation, whereby the film is highly super-exposed and developed by a devel- 35 oper which also limits the blackening automatically.

From the three negatives thus obtained the screened work copy may i. i. be produced in the following manner:

40 The three negatives and an. unexposed sensitive film are superimposed so that in the direction of the printing light the films are lying behind each other in the sequence: first continuous tone negative, screened negative, sec- 45 nd continuous-tone negative, unexposed film. Thereafter the unexposed film is exposed through the three negatives. The second continuous- 1 tone negative is removed and'the exposure repeated. The twice exposed film is then devel- 50' oped, fixed,'toned down, until the highest lights are free from dots, and finally treated by means 01" an intensifier, so that the finest dots'are sufliciently covered or'blackened for the purpose of Pfl E- '5 In the described method the quality of the film needs no particular care.

reproduction essentially depends thereupon, that during the mentioned intensifying treatment the finest dots are really and sufliciently covered or blackened without affecting the contrast between the different tone or tint values of the screened 5 work copy;

I have found that the intensifying treatment can be carried through in a particularly rapid and reliable manner by utilizing an intensifier composed of a solution of about 3 g. mercuric chloride in 100 com. water and of a solution of about 10 g. potassium iodide in 100 com. water. The composition of the intensifier is efiected by gradually adding the aqueous solution of potas-' sium iodide to the aqueous solution of mercuric l5 chloride until the dense yellow-red sediment initially created dissolves. In case that a too large quantity of the potassium iodide solution has been added, one may gradually add a small quantity of mercuric chloride solution until the intensifier liquid begins to-become turbid. A further advantage of the intensifier consists therein, that it absolutely is insensible towards fixingagents so that the washing of the fixed work copy What I claim is:

1. The process of producing a screened work copy of an original to bereproduced, which proc-' ess comprises producing a screened negative having the shadow dots thereon larger than normal and the lights closed more than normal, and producing two continuous-tone negatives, one of which continuous-tone negatives controls the tone values of the screened negative within the lights and the other within the shadows, one of 'said continuous-tone negatives being underexposed and the other being overexposed, exposing through the said three negatives the light sensitiye transfer element or carrier for transferring the-screened work copy, developing, fixing and 40 toning down said carrier or element, until the highest lights are free from dots, and finally intensifying the exposed carrier or element in order to blacken the finest dots, by the utilization of an intensifier composed of an aqueous solution of 3 g. mercuric chloride in com. water mixed with an aqueous solution of 10 g. potassium 3 an aqueous solution of mercuric chloride and potassium iodide.

3. The process for producing a screened work copy of an original to be reproduced, which process comprises preparing a main or screened negm ative of said original having the shadow dots thereon larger than normal and the lights closed more than normal, preparing a first continuoustone negative by subjecting a sensitive film to very short exposure, developing andfixing said continuous-tone negative, preparing a second continuous-tone negative by over-exposing a sensitive film, developing and fixing the second continuous-tone negative, superimposing the three negatives thusproduced upon an unexposed film, exposing the unexposed film through the superimposed negatives, removing the second continnous-tone negative and again exposing the re-'- maining superimposed negatives, developing, fixing and toning down the twice exposed film, and

' tensifier liquid isat the finally subjecting the exposed film to the action of an intensifier composed oi? a solution of 3 g. mercuric chloride in 100 com. 01! water mixed with a solution of 10 g. potassium iodide in 100 com. of water, the proportions of the solution of said mixture being so defined that the intensifier liquid is at the limit of turbidity.

4. The process for producing a screened work copy of an original to be reproduced, which process comprises preparing a main or screened negative of the original having the shadow dots thereon larger than normal and the lights closed more than normal, preparing a first continuoustone negative of the original to be reproduced wherein the lights have a delicate blackening by subjecting a sensitive film to very short exposure, developing and fixing said continuous-tone negative, preparing a second continuous-tone negative of the original by over-exposing a sensitive film, developing and fixing the second continuous-to'ne negative, superimposing the three negatives thus produced upon an unexposed film with the screened negative intermediate the continuous-tone negatives, exposing the unexposed film through the superimposed negatives, removing the second continuous-tone negative and again exposing the superimposed negatives, developing, fixing and toning down the twice exposed film, and finally subjecting the exposed film to the action of an intensifier composed of a solution of 3 g. mercuric chloride in 100 com. of water mixed with a solution of 10 g. potassium iodide tion of said mixture being so defined that the inlimit of turbidity.

WILHELM SCHUPP.

in 100 com. of water, the proportions of the solu- 

